小脳橋角部脂肪腫の1例

Cerebellopontine Angle Lipoma:Case Report

　はじめに

　頭蓋内脂肪腫は稀な脳腫瘍である。さらに小脳橋角部腫瘍の大多数が聴神経腫瘍であることを考えると同部の脂肪腫は非常に稀であるといえよう。今回われわれは，左慢性中耳炎の術前検査，特に画像診断にて左小脳橋角部腫瘍の疑いを持ち，手術により左小脳橋角部脂肪腫と診断された症例を経験した。この小脳橋角部脂肪腫は，国内外の剖検例，臨床例を合わせても現在までに23症例が報告されているにすぎず，極めて稀な疾患であると考える。そこで，今回，自験例の詳細を報告し，特に本症の画像診断上の問題点について文献的考察を加えた。

Intracranial lipoma seems to be very rare, especially in the cerebellopontine angle. Only 23 cases have been reported. A 23-year-old female complained of a progressive hearing loss in the left ear after swimming, and was diagnosed as having a chronic otitis media. On microscopic examination, a central perforation in the left tympanic membrane was found. A pure tone audiogram showed 57.5 dB hearing level of mixed type in the left ear. X-ray showed dilata-tion of the internal auditory canal of the left ear. Although cerebellopontine angle tumor was suspected, a left tympanoplasty was carried out to control infection in the middle ear. After the operation, the further examination about the internal auditory canal dilatation was done. CT showed a low density area and T₁-weighted MRI showed a high signal area in the left cerebel-lopontine angle. Lipoma of the left cerebellopon-tine angle was suspected, and the patient was referred to neurosurgical department. The patient underwent a posterior fossa-craniotomy, and a yellowish tumor in the left cerebellopontine angle was removed. Subsequently the tumor was con-firmed as a lipoma histologically.